Ediacaran, Cambrian, Ordovician, Silurian and Permian shales of the Upper Yangtze Platform, South China: Deposition, thermal maturity and shale gas potential

Zhang, Qian; Littke, Ralf; Zieger, Laura; Shabani, Mohammadebrahim; Tang, Xuan; Zhang, Jinchuan

doi:10.1016/j.coal.2019.103281

Cited by 37 publications

(11 citation statements)

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“…While numerous studies were performed to characterize storage properties of the Wufeng-Longmaxi shales (Yang et al 2015(Yang et al , 2016(Yang et al , 2017Wang et al 2016), only a few studies thus far focused on shales from the Ediacaran (Chen et al 2016;Yang et al 2020). These shales, though extremely high in thermal maturity (approximately 4.0% in equivalent vitrinite reflectance), are rich in organic matter (TOC content of up to 8.0 wt.%) and widely distributed in the area of the Upper Yangtze platform with thicknesses of 200 to 900 m. The well-studied Silurian Longmaxi Shale in the Sichuan Basin has a lower thermal maturity (2.0-3.2%), smaller thickness from 100 to 500 m, exhibits high TOC contents (up to 8.3 wt.%) as well as porosity (3.4-8.2%) (Zou et al 2014;Yang et al 2015;Zhang et al 2019).…”

Section: Article Highlightsmentioning

confidence: 99%

“…b Fig. 2 Litho-and chrono-stratigraphy of the Upper Yangtze Platform (modified after Zhai.1987 andZhang et al 2019) Solid bitumen reflectances were taken from Zhang et al (2019) and converted to vitrinite reflectances by using Eq. 1 after Mählmann and Frey (2012) The excess sorption amount (n excess ) corresponds to the difference between the entire amount of gas transferred from the reference cell into the sample cell (n trans ) and the amount of ''free'' gas occupying the void volume (V void ) of the sample cell.…”

Section: High-pressure Methane Sorption Measurementsmentioning

confidence: 99%

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Pore structure and sorption capacity investigations of Ediacaran and Lower Silurian gas shales from the Upper Yangtze platform, China

Gaus

Seemann

et al. 2021

Geomech. Geophys. Geo-energ. Geo-resour.

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The shale gas potential of Ediacaran and Lower Silurian shales from the Upper Yangtze platform is assessed in this study with a focus on the contributions of clay minerals and organic matter to sorption capacity. For this purpose, a multidisciplinary assessment was carried out using petrophysical, mineralogical, petrographic and geochemical methods. In terms of TOC contents (4.2%), brittle mineral contents (68.6%) and maximum gas storage capacities (0.054–0.251 mmol/g) Ediacaran shales from this study show comparable properties to other producing shale gas systems although the thermal maturity is extremely high (VRr = 3.6%). When compared to lower Silurian shales from the same region, it is evident that (1) deeper maximum burial and (2) a lack of silica-associated preservation of the pores resulted in a relatively lower mesopore volume, higher micropore volume fraction and lower overall porosity (Ediacaran shales: 1.4–4.6%; Silurian shales: 6.2–7.4%). Gas production is therefore retarded by poor interconnectivity of the pore system, which was qualitatively demonstrated by comparing experimental gas uptake kinetics. TOC content exhibits a prominent control on sorption capacity and micropore volume for both shales. However, different contributions of clay minerals to sorption capacity were identified. This can partly be attributed to different clay types but is likely also related to burial-induced recrystallisation and different origins of illite. Additionally, it was shown that variations in sorption capacity due to incorrect estimates of clay mineral contribution are in the same range as variations due to differences in thermal maturity. Article highlights Pore structure and gas storage characteristics are evaluated for the first time for Ediacaran Shales from the Upper Yangtze platform Due to a lower free gas storage capacity and diffusivity, the Ediacaran shale can be regarded as a less favorable shale gas prospect when compared to the Silurian shale Clay mineral contribution to sorption capacity is evaluated taking clay mineralogy into consideration Maturity-related changes of organic matter sorption capacity have been discussed on the basis of a compiled data set

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Section: Article Highlightsmentioning

confidence: 99%

Section: High-pressure Methane Sorption Measurementsmentioning

confidence: 99%

Pore structure and sorption capacity investigations of Ediacaran and Lower Silurian gas shales from the Upper Yangtze platform, China

Gaus

Seemann

et al. 2021

Geomech. Geophys. Geo-energ. Geo-resour.

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“…Due to the existence of the Huangling paleouplift, the ancient burial depth of the Niutitang shale distributed in its periphery is only 6500 m. 9 Geofluids paleouplift, the Yichang Slope Belt, the Zigui Depression, and many other tectonic units (Figure 12). At present, shale gas exploration has focused mainly on the Sinian Doushantuo Formation and the Niutitang Formation by the China Geological Survey, in the southeastern margin of the Huangling paleouplift [33,39]. The Huangling paleouplift was formed during the Late Jurassic to Early cretaceous with a monoclinal structure trending SE [40].…”

Section: Geofluidsmentioning

confidence: 99%

Slope Belts of Paleouplifts Control the Pore Structure of Organic Matter of Marine Shale: A Comparative Study of Lower Cambrian Rocks in the Sichuan Basin

et al. 2021

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Extensive exploration of the marine shale of the Niutitang Formation in south China has been conducted. However, exploration and development results have varied considerably in different areas. For example, the Niutitang shale in Jingyan City (Southwestern Sichuan Basin) produces a large amount of gas with a long period of stable production. In contrast, most development wells in the Niutitang shale in Chongqing City do not produce gas. Scanning electron microscopy images showed that the organic matter (OM) pore development in the Niutitang shale in Jingyan is abundant, large in size, and are well connected. In contrast, OM pores in the Niutitang shale in Chongqing are rarely observed. OM pore development of the Jingyan and Chongqing shales is mainly controlled by thermal maturity as shown by equivalent vitrine reflectance determinations. The moderate thermal maturity has resulted in the development of a large number of OM pores in the Niutitang shale in Jingyan, whereas the high thermal maturity of the Niutitang shale in Chongqing has led to the destruction of most of the OM pores. Due to the existence of ancient uplift, the shale was buried shallowly in the process of hydrocarbon generation evolution, and the shale avoided excessive thermal evolution and retained appropriate thermal maturity. In the Jingyan area, due to its location near the central uplift in the Sichuan Basin, the Niutitang shale deposited nearby avoided excessive evolution, and a large number of OM pores were retained in the reservoir.

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“…The connectivity of pores is related to the rising rate of the adsorption line; the faster the rise, the better the connectivity of pores. The regular degree of pore shape is related to the size of the hysteresis loop; the smaller the hysteresis loop, the greater the regularity (Thommes et al 2015;Zhang et al 2016). This indicates that the pore structure of the BD shale sample is mainly composed of open pores such as parallel plate-shaped pores and slit-shaped pores that open at both ends, that is, micro-fractures that are connected to each other with a large fracture length.…”

Section: C Effect Of Slip Rheological Deformation On Shale Pore Stmentioning

confidence: 99%

“…The outstanding achievements in exploration and exploitation of shale gas in North America has led to increased shale gas exploration worldwide (Stephenson, 2016). Compared with North America, Southern China has experienced multi-stage tectonic activities, with problems such as the development of fault systems, strong tectonic deformation, complex surface conditions and complex in situ stress state (Zou et al 2010;Han et al 2013;Tang et al 2017;Wan et al 2017;Zhang et al 2019). In the complex structural areas of Southern China, shale gas has developed rapidly and achieved world-renowned results; several shale gas demonstration areas have been built, such as the Fuling Shale Gas Field and Weiyuan Shale Gas Field (Wang et al 2013;Luo et al 2016;Ma & Xie, 2018).…”

Section: Introductionmentioning

confidence: 99%

Influence of differential structural deformation on shale reservoirs: a case study of the lower Silurian Longmaxi Shale in north Guizhou, Southern China

Gu¹,

Xu³

et al. 2020

Geol. Mag.

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Southern China is affected by multi-stage tectonic activities, with strong fold deformation, complex fault systems and poor shale gas preservation conditions. Here, we used shale samples from the lower Silurian Longmaxi shale in the complex tectonic area of Southern China, to study the relationship between differential structural deformation, and pore structure and adsorption capacity. According to the deformation mechanism of the shale, it is further divided into brittle-slip rheological deformation (BD) and ductile-slip rheological deformation (DD). The results show that all micro-fractures can be observed under scanning electron microscopy in deformed shale samples, but in shale samples with different types of rheological deformation, the micro-fractures have large differences in scale, fracture length and lateral connectivity. The micro-fractures developed in DD shales are small in scale and short in fracture length, but have strong local connectivity. In contrast, brittle minerals are more developed in BD shales, and interlayer shearing has formed micro-fractures with large fracture length and good lateral connectivity, which is beneficial for later fracturing. In these two types of deformed shales, pores in organic matter are rare, and sporadic organic pores have small pore size and poor connectivity. The total pore volume (1.8–2.4 × 10−2 cm3 g–1) of BD shale samples is higher than that of DD shale samples (0.8–1.6 × 10−2 cm3 g–1). There is a positive correlation between total pore volume and quartz content. In addition, the specific surface area (12–18 m2 g–1) of DD shale samples is larger than that of BD shale samples (6–12 m2 g–1).

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Ediacaran, Cambrian, Ordovician, Silurian and Permian shales of the Upper Yangtze Platform, South China: Deposition, thermal maturity and shale gas potential

Cited by 37 publications

References 91 publications

Pore structure and sorption capacity investigations of Ediacaran and Lower Silurian gas shales from the Upper Yangtze platform, China

Pore structure and sorption capacity investigations of Ediacaran and Lower Silurian gas shales from the Upper Yangtze platform, China

Slope Belts of Paleouplifts Control the Pore Structure of Organic Matter of Marine Shale: A Comparative Study of Lower Cambrian Rocks in the Sichuan Basin

Influence of differential structural deformation on shale reservoirs: a case study of the lower Silurian Longmaxi Shale in north Guizhou, Southern China

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